Automated sample analysis devices have been developed to reduce human error in the performance of quantitative assays. Instruments of this type typically comprise apparatus used in industry and by laboratories to process hundreds or thousands of assays in a single day. These instruments are expensive and generally require the attention of a skilled technician for proper operation and to insure reliability of assay results.
A typical instrument used in high volume test environments is a large high throughput system offered by Olympus Clinical Instruments Division, under the trademark "REPLY." The "REPLY" instrument is a large system requiring approximately 7 feet by 11 feet of dedicated floor space and handles 400-600 tests per hour in a random access operating mode typical of moderate to high volume routine testing. The "REPLY" system requires 20 minutes warm-up time before being available to do testing. Additionally, trained technicians must install appropriate reagents, manage waste volumes and prime the system prior to initiating assays. In this and similar large test systems, proper use requires a high skill level and extensive training of operators to realize these benefits. Set up and calibration for all the reagents required to perform all anticipated assays from a large menu of test types (typically 70 different assays) must be accomplished prior to the system being available to perform all tests. This is inconvenient for less frequently ordered tests.
The operator of the above apparatus must prepare and replenish the reagents and monitor the apparatus' proper operation. In addition, the technician must be sufficiently competent to reconfigure the apparatus to perform different assays and various classes of assays.
In addition, although the apparatus described above is useful when conducting homogeneous assays, it is not well suited to conducting heterogeneous assays. Heterogeneous immunoassays, such as competitive assays, sandwich assays and sequential assays (such as those used for determination of the presence of hepatitis-B virus or the antigen to Human Immunodeficiency Virus), require long incubation times and separation of bound from free label, involving one or more washing steps which exceeds the capability of such apparatus.
For performing homogeneous assays, automated apparatus of the type described above have been very successful in large laboratories. However, such apparatus is not satisfactory for use in physicians' offices, by untrained personnel, or for processing a small number of samples. For this purpose, self-contained assay cartridges have been developed which contain all of the required reagents for performing an assay.
Such a cartridge for homogeneous assays is described in European Patent Application Publication No. 0,160,282 filed by Abbott Laboratories. An apparatus for processing the cartridge is described in European Patent Publication No. 0,160,901, also filed by Abbott Laboratories. The cartridge described in these applications is adapted to be received on a centrifuge which rotates about a rotation axis. The centrifuge is provided with axially displaced, secondary rotation axes to rotate the cartridge 90 degrees within the plane of the centrifuge. This compound, rotary motion is required to cause-the reagents and patient sample to be appropriately metered and dispensed into various compartments. The cartridge is mechanically complex, relatively large and is expensive to manufacture.
In addition, because of the multi-dimensional type of motions required to process the contents of the cartridge, the apparatus described in EP 160,901 is also quite mechanically complex, and potentially unreliable. Further, this apparatus is not compact and is characterized by a significant noise level during operation.
Therefore, there is a need in the art for an automated apparatus capable of conducting both homogeneous and heterogeneous assays, which is compact, reliable and simple to operate. The apparatus should also be quiet during operation, and be capable of analyzing a variable number of processed or unprocessed samples for different tests without substantial modification of the instrument. The apparatus should be capable of using self-contained assay cartridges which can be automatically calibrated. The present invention fulfills this need and further provides other related advantages.